NEW YORK — An undercover police detective who fired the first bullets in a 50-shot barrage that killed an unarmed New York City man as he left his bachelor party has been fired and three other officers involved in the slaying will resign, ending a disciplinary process that dragged on for nearly 5 1/2 years.

Police Commissioner Raymond Kelly made the decision to push the four officers out Friday, four months after a department administrative trial judge concluded that detective Gescard Isnora acted improperly in the 2006 killing of the would-be groom, Sean Bell.

NYPD spokesman Paul Browne said Friday that "there was nothing in the record to warrant overturning the decision."

Isnora and fellow detectives Marc Cooper and Michael Oliver and Lt. Gary Napoli were widely condemned and brought up on criminal charges following the shooting outside a Queens nightclub, but they were acquitted on all counts at their 2008 trial.

Bell was black; the officers involved in the shooting were black, white and Hispanic. The shooting drew national attention and reopened questions of race and whether black men were unfairly targeted by police, but critics eventually came to focus more on the use of deadly force.

The detectives, who had been monitoring the club for drug activity, decided to stop Bell and his friends after they left the nightspot and got into their car following a verbal altercation with another group of men. Isnora said he believed they were in the vehicle to retrieve a gun. In fact, the men were unarmed, but Isnora began shooting when the driver hit the gas and rammed a police van.

Isnora fired 11 shots into the car. The 23-year-old Bell was killed and two friends seriously wounded. Cooper and Oliver also fired shots. Another detective who fired his gun, Paul Headley, has already resigned, while a fifth shooter was ruled by the administrative judge not to have acted improperly. Napoli was a supervisor at the scene.

The firing means that Isnora will lose his pension and health care benefits.

Isnora's lawyer, Philip Karasyk, told The New York Times () that the decision to fire the officer was "extremely disheartening and callous and sends an uncaring message to the hard-working officers of the New York Police Department who put their lives on the line every day." http://nyti.ms/GU1fZz

Mike Palladino, president of the Detectives' Endowment Association, said Saturday that the union and its lawyers were reviewing the decision to see if Isnora has any legal recourse.

"The decision is demoralizing and it's unsetting for all members of the NYPD," Palladino said. "The message is that you could be in a life-or-death situation, act within the law, be justified by the courts and still lose everything – your livelihood as well as your retirement."